U.S. patent number 10,854,806 [Application Number 15/894,169] was granted by the patent office on 2020-12-01 for vibrating device.
This patent grant is currently assigned to TDK CORPORATION. The grantee listed for this patent is TDK CORPORATION. Invention is credited to Kaoru Kijima, Kazushi Tachimoto, Tatsuya Taki.
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United States Patent |
10,854,806 |
Kijima , et al. |
December 1, 2020 |
Vibrating device
Abstract
A vibrating device includes a piezoelectric element, a wiring
board electrically connected with the piezoelectric element, and a
diaphragm including a metal. The piezoelectric element and the
wiring board are bonded to the diaphragm. The piezoelectric element
includes a piezoelectric element body, a plurality of internal
electrodes, and a plurality of external electrodes. The
piezoelectric element body has a first principal plane and a second
principal plane opposed to each other. The plurality of internal
electrodes is disposed in the piezoelectric element body. The
internal electrodes are opposed to each other in a direction in
which the first principal plane and the second principal plane are
opposed. The plurality of external electrodes is disposed on the
first principal plane, and is electrically connected with
corresponding internal electrodes, of the plurality of internal
electrodes. The wiring board has a resin film and a plurality of
conductors.
Inventors: |
Kijima; Kaoru (Tokyo,
JP), Taki; Tatsuya (Tokyo, JP), Tachimoto;
Kazushi (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TDK CORPORATION |
Tokyo |
N/A |
JP |
|
|
Assignee: |
TDK CORPORATION (Tokyo,
JP)
|
Family
ID: |
1000005217096 |
Appl.
No.: |
15/894,169 |
Filed: |
February 12, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180233652 A1 |
Aug 16, 2018 |
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Foreign Application Priority Data
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|
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Feb 13, 2017 [JP] |
|
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2017-024314 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
41/0474 (20130101); H01L 41/09 (20130101); H01L
41/187 (20130101); H01L 41/083 (20130101); H01L
41/0477 (20130101); H01L 41/0475 (20130101) |
Current International
Class: |
H01L
41/047 (20060101); H01L 41/083 (20060101); H01L
41/187 (20060101); H01L 41/09 (20060101) |
Field of
Search: |
;310/311-371,800 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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H04-70100 |
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Mar 1992 |
|
JP |
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H10-315485 |
|
Dec 1998 |
|
JP |
|
2006-150808 |
|
Jun 2006 |
|
JP |
|
2016-051895 |
|
Apr 2016 |
|
JP |
|
Primary Examiner: Dougherty; Thomas M
Attorney, Agent or Firm: Oliff PLC
Claims
What is claimed is:
1. A vibrating device comprising: a piezoelectric element; a wiring
board electrically connected with the piezoelectric element; and a
diaphragm including a metal and to which the piezoelectric element
and the wiring board are bonded, wherein the piezoelectric element
includes a piezoelectric element body including a piezoelectric
material and having a first principal plane and a second principal
plane opposed to each other, a plurality of internal electrodes
disposed in the piezoelectric element body, and opposed to each
other in a direction in which the first principal plane and the
second principal plane are opposed to each other, and a plurality
of external electrodes disposed on the first principal plane, and
electrically connected with corresponding internal electrodes, of
the plurality of internal electrodes, the wiring board includes a
resin film bonded to the diaphragm, and a plurality of conductors
disposed on the resin film, and electrically connected with
corresponding external electrodes, of the plurality of external
electrodes, the plurality of external electrodes is separated from
all of edges of the first principal plane as viewed from the
direction, and conductors electrically connected with the plurality
of internal electrodes are not disposed on the second principal
plane of the piezoelectric element body, and the second principal
plane and the diaphragm are bonded to each other.
2. The vibrating device according to claim 1, wherein the
piezoelectric element body further includes a side surface adjacent
to the first principal plane and the second principal plane, and
the plurality of internal electrodes is not exposed to the side
surface.
3. The vibrating device according to claim 1, wherein the plurality
of external electrodes is separated from all of edges of the
plurality of internal electrodes as viewed from the direction.
4. The vibrating device according to claim 1, wherein the plurality
of internal electrodes includes a first internal electrode and a
second internal electrode, and the plurality of external electrodes
includes a plurality of first external electrodes electrically
connected with the first internal electrode, and adjacent to each
other on the first principal plane, and a plurality of second
external electrodes electrically connected with the second internal
electrode, and adjacent to each other on the first principal
plane.
5. The vibrating device according to claim 4, wherein the first
principal plane has a rectangular shape as viewed from the
direction, and the plurality of first external electrodes and the
plurality of second external electrodes are disposed along only one
side of the edges of the first principal plane.
6. The vibrating device according to claim 4, further comprising: a
first conductive resin having one end portion connected with the
plurality of first external electrodes and another end portion
connected with corresponding conductors, of the plurality of
conductors; and a second conductive resin having one end portion
connected with the plurality of second external electrodes and
another end portion connected with corresponding conductors, of the
plurality of conductors.
7. The vibrating device according to claim 2, wherein the side
surface of the piezoelectric element body is bonded to the
diaphragm.
Description
TECHNICAL FIELD
One aspect of the present invention relates to a vibrating
device.
BACKGROUND
Known vibrating devices include a piezoelectric element and a
diaphragm made of glass and bonded to the piezoelectric element
(for example, Japanese Unexamined Patent Publication No.
04-070100).
SUMMARY
In the vibrating device described in Japanese Unexamined Patent
Publication No. 04-070100, the diaphragm is made of glass.
Therefore, the Q value and the strength of the diaphragm are
relatively low, and improvement of the displacement amount is
difficult.
One aspect of the present invention is to provide a vibrating
device with an improved displacement amount.
A vibrating device according to one aspect of the present invention
includes a piezoelectric element, a wiring board electrically
connected with the piezoelectric element, and a diaphragm including
a metal. The piezoelectric element and the wiring board are bonded
to the diaphragm. The piezoelectric element includes a
piezoelectric element body, a plurality of internal electrodes, and
a plurality of external electrodes. The piezoelectric element body
includes a piezoelectric material, and has a first principal plane
and a second principal plane opposed to each other. The plurality
of internal electrodes is disposed in the piezoelectric element
body. The internal electrodes are opposed to each other in a
direction in which the first principal plane and the second
principal plane are opposed. The plurality of external electrodes
is disposed on the first principal plane, and is electrically
connected with corresponding internal electrodes, of the plurality
of internal electrodes. The wiring board has a resin film and a
plurality of conductors. The resin film is bonded to the diaphragm.
The plurality of conductors is disposed on the resin film, and is
electrically connected with corresponding external electrodes, of
the plurality of external electrodes. The plurality of external
electrodes is separated from all of edges of the first principal
plane as viewed from the direction. Conductors electrically
connected with the plurality of internal electrodes are not
disposed on the second principal plane of the piezoelectric element
body. The second principal plane and the diaphragm are bonded.
In the vibrating device according to the one aspect of the present
invention, the diaphragm includes a metal. The diaphragm including
a metal has a higher Q value and strength than a diaphragm made of
glass. Therefore, a displacement amount of the vibrating device is
improved.
In the one aspect of the present invention, the plurality of
external electrodes is disposed on the first principal plane, not
on the second principal plane bonded to the diaphragm. Conductors
electrically connected with the plurality of internal electrodes
are not disposed on the second principal plane. The plurality of
external electrodes is separated from all of edges of the first
principal plane as viewed from the direction. As a result, even
when the diaphragm includes a metal, the piezoelectric element
(external electrode) and the diaphragm are electrically insulated.
Therefore, a short circuit between the piezoelectric element and
the diaphragm is less likely to occur, and electrical reliability
of the vibrating device is improved.
The piezoelectric element body may further have side surface
adjacent to the first principal plane and the second principal
plane. The plurality of internal electrodes may not be exposed to
the side surface. In this case, the piezoelectric element and the
diaphragm are more reliably electrically insulated.
The plurality of external electrodes may be separated from all of
edges of the plurality of internal electrodes as viewed from the
direction. In this case, the plurality of external electrodes is
further separated from the edges of the first principal plane as
viewed from the direction. As a result, the external electrodes and
the diaphragm are more reliably electrically insulated.
The plurality of internal electrodes may include a first internal
electrode and a second internal electrode. In this case, the
plurality of external electrodes may include a plurality of first
external electrodes and a plurality of second external electrodes.
The plurality of first external electrodes may be electrically
connected with the first internal electrode, and adjacent to each
other on the first principal plane. The plurality of second
external electrodes may be electrically connected with the second
internal electrode, and adjacent to each other on the first
principal plane. In this case, electrical connection reliability
between the piezoelectric element and the wiring board is
improved.
The first principal plane may have a rectangular shape as viewed
from the direction. In this case, the plurality of first external
electrodes and the plurality of second external electrodes may be
disposed along only one side of the edges of the first principal
plane. In this case, electrical connection between the plurality of
first external electrodes and the wiring board is easily realized
and electrical connection between the plurality of second external
electrodes, and the wiring board is easily realized.
The vibrating device according to the one aspect of the present
invention may further include a first conductive resin and a second
conductive resin. The first conductive resin may have one end
portion connected with the plurality of first external electrodes
and another end portion connected with corresponding conductors, of
the plurality of conductors. The second conductive resin may have
one end portion connected with the plurality of second external
electrodes and another end portion connected with corresponding
conductors, of the plurality of conductors. In this case,
electrical connection between the plurality of first external
electrodes and the conductors corresponding to the plurality of
first external electrodes is easily realized. Further, electrical
connection between the plurality of second external electrodes and
the conductors corresponding to the plurality of second external
electrodes is easily realized.
The side surface of the piezoelectric element body may be bonded to
the diaphragm. In this case, bonding strength between the
piezoelectric element and the diaphragm is improved. As a result,
displacement of the piezoelectric element is efficiently
transmitted to the diaphragm.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a vibrating device according to an
embodiment;
FIG. 2 is a diagram illustrating a sectional configuration of the
vibrating device according to the present embodiment;
FIG. 3 is a diagram illustrating a sectional configuration of the
vibrating device according to the present embodiment;
FIG. 4 is a diagram illustrating a sectional configuration of the
vibrating device according to the present embodiment;
FIG. 5 is an exploded perspective view illustrating a configuration
of a piezoelectric element; and
FIG. 6 is a plan view of the piezoelectric element.
DETAILED DESCRIPTION
Hereinafter, embodiments will be described in detail with reference
to the accompanying drawings. Note that, in the description, the
same reference sign is used for the same elements or elements
having the same function, and redundant description is omitted.
A configuration of a vibrating device 1 according to the present
embodiment will be described with reference to FIGS. 1 to 6. FIG. 1
is a plan view of a vibrating device according to an embodiment.
FIGS. 2, 3, and 4 are diagrams illustrating a sectional
configuration of the vibrating device according to the present
embodiment. FIG. 5 is an exploded perspective view illustrating a
configuration of a piezoelectric element. FIG. 6 is a plan view of
the piezoelectric element.
As illustrated in FIG. 1, the vibrating device 1 includes a
piezoelectric element 10, a wiring board 40, and a diaphragm 50.
The piezoelectric element 10 includes a piezoelectric element body
11 and a plurality of external electrodes 13 and 15.
The piezoelectric element body 11 has a rectangular parallelepiped
shape. The piezoelectric element body 11 has a pair of principal
planes 11a and 11b opposed to each other and four side surfaces
11c. The rectangular parallelepiped shape includes a rectangular
parallelepiped shape with chamfered corner portions and ridge
portions, and a rectangular parallelepiped shape with rounded
corner portions and ridge portions. The principal planes 11a and
11b have a rectangular shape. In the present embodiment, the
principal planes 11a and 11b have a square shape.
The direction in which the pair of principal planes 11a and 11b are
opposed is a first direction D1. The first direction D1 is also a
direction orthogonal to the principal planes 11a and 11b. The four
side surfaces 11c extend in the first direction D1 in such a way as
to connect the pair of principal planes 11a and 11b. The principal
planes 11a and 11b and the side surfaces 11c are indirectly
adjacent via a ridge line portion. The length of the piezoelectric
element body 11 in the first direction D1 (the thickness of the
piezoelectric element body 11) is, for example, 100 .mu.m.
As illustrated in FIG. 5, the piezoelectric element body 11
includes a plurality of piezoelectric layers 17a, 17b, 17c, and 17d
laminated in the first direction D1. In the present embodiment, the
piezoelectric element body 11 includes the four piezoelectric
layers 17a, 17b, 17c, and 17d. In the piezoelectric element body
11, the direction in which the plurality of piezoelectric layers
17a, 17b, 17c, and 17d is laminated accords with the first
direction D1.
Each of the piezoelectric layers 17a, 17b, 17c, and 17d contains a
piezoelectric material. In the present embodiment, each of the
piezoelectric layers 17a, 17b, 17c, and 17d contains a
piezoelectric ceramic material. Examples of the piezoelectric
ceramic material include PZT[Pb (Zr, Ti)O.sub.3], PT(PbTiO.sub.3),
PLZT[(Pb, La)(Zr, Ti)O.sub.3], and barium titanate (BaTiO.sub.3).
Each of the piezoelectric layers 17a, 17b, 17c, and 17d is composed
of a sintered body of a ceramic green sheet containing the
above-described piezoelectric ceramic material, for example. In the
actual piezoelectric element body 11, the piezoelectric layers 17a,
17b, 17c, and 17d are integrated to such an extent that boundaries
between each two of the piezoelectric layers 17a, 17b, 17c, and 17d
cannot be recognized.
The piezoelectric layer 17a has the principal plane 11a. The
piezoelectric layer 17d has the principal plane 11b. The
piezoelectric layers 17b and 17c are located between the
piezoelectric layer 17a and the piezoelectric layer 17d. The
thickness of the piezoelectric layer 17a or 17d is smaller than the
thickness of the piezoelectric layer 17b or 17c. The thickness of
the piezoelectric layer 17a or 17d is, for example, 33 .mu.m. The
thickness of the piezoelectric layer 17b or 17c is, for example, 16
.mu.m.
As illustrated in FIGS. 2, 3, 4, and 5, the piezoelectric element
10 includes a plurality of internal electrodes 19, 21, and 23
disposed in the piezoelectric element body 11. In the present
embodiment, the piezoelectric element 10 includes the three
internal electrodes 19, 21, and 23.
Each of the internal electrodes 19, 21, and 23 contain a conductive
material. As the conductive material, Ag, Pd, or an Ag--Pd alloy is
used, for example. Each of the internal electrodes 19, 21, and 23
is composed as a sintered body of a conductive paste containing the
above-described conductive material. Each of the internal
electrodes 19, 21, and 23 has an approximately rectangular shape
(for example, approximately square shape).
The internal electrodes 19, 21, and 23 are disposed at different
positions (layers) in the first direction D1. The internal
electrode 19 and the internal electrode 21 are opposed to each
other with a space in the first direction D1. The internal
electrode 21 and the internal electrode 23 are opposed to each
other with a space in the first direction D1. The internal
electrode 19 is located between the piezoelectric layer 17a and the
piezoelectric layer 17b. The internal electrode 21 is located
between the piezoelectric layer 17b and the piezoelectric layer
17c. The internal electrode 23 is located between the piezoelectric
layer 17c and the piezoelectric layer 17d.
The internal electrodes 19, 21, and 23 are not exposed to a surface
of the piezoelectric element body 11. That is, the internal
electrodes 19, 21, and 23 are not exposed to the side surface 11c.
Therefore, as illustrated in FIG. 6, each of the internal
electrodes 19, 21, and 23 is separated from all of edges (four
sides) of the principal plane 11a or 11b as viewed from the first
direction D1.
The plurality of external electrodes 13 and 15 is disposed on the
principal plane 11a. The external electrode 13 includes a plurality
of external electrodes 13a and 13b. In the present embodiment, the
external electrode 13 includes the two external electrodes 13a and
13b. The external electrode 15 includes a plurality of external
electrodes 15a and 15b. In the present embodiment, the external
electrode 15 includes the two external electrodes 15a and 15b. Each
of the external electrodes 13a, 13b, 15a, and 15b has an
approximately elliptical shape as viewed from the first direction
D1.
Each of the external electrode 13 and 15 (each of the external
electrodes 13a, 13b, 15a, and 15b) contains a conductive material.
As the conductive material, Ag, Pd, or an Ag--Pd alloy is used, for
example. Each of the external electrodes 13 and 15 is composed as a
sintered body of a conductive paste containing the above conductive
material.
As illustrated in FIG. 6, each of the external electrodes 13 and 15
(each of the external electrodes 13a, 13b, 15a, and 15b) is
separated from all of edges (four sides) of the principal plane 11a
or 11b as viewed from the first direction D1. As illustrated in
FIG. 6, each of the external electrodes 13 and 15 (each of the
external electrodes 13a, 13b, 15a, and 15b) is separated from all
of edges (four sides) of the internal electrode 19, 21, or 23 as
viewed from the first direction D1.
The external electrode 13a and the external electrode 13b are
adjacent to each other. The external electrode 15a and the external
electrode 15b are adjacent to each other. The four external
electrodes 13a, 13b, 15a, and 15b are disposed along only one side
of the principal plane 11a. The external electrode 13b and the
external electrode 15a are adjacent to each other.
The external electrodes 13a and 13b are electrically connected with
a connection conductor 25 through a plurality of via conductors 31,
respectively. The connection conductor 25 is located in the same
layer as the internal electrode 19. The connection conductor 25 is
located between the piezoelectric layer 17a and the piezoelectric
layer 17b. The internal electrode 19 and the connection conductor
25 are separated from each other. The connection conductor 25 is
opposed to the external electrodes 13a and 13b in the first
direction D1. The plurality of via conductors 31 is connected with
the external electrodes 13a and 13b and the connection conductor
25.
The external electrodes 15a and 15b are electrically connected with
the internal electrode 19 through a plurality of via conductors 33,
respectively. The internal electrode 19 is opposed to the external
electrodes 15a and 15b in the first direction D1. The plurality of
via conductors 33 is connected with the external electrodes 15a and
15b and the internal electrode 19.
The connection conductor 25 is electrically connected with the
internal electrode 21 through a plurality of via conductors 35. The
connection conductor 25 is opposed to the internal electrode 21 in
the first direction D1. The plurality of via conductors 35 is
connected with the connection conductor 25 and the internal
electrode 21.
The internal electrode 19 is electrically connected with a
connection conductor 27 through a plurality of via conductors 37.
The connection conductor 27 is located in the same layer as the
internal electrode 21. The connection conductor 27 is located
between the piezoelectric layer 17b and the piezoelectric layer
17c. The internal electrode 21 and the connection conductor 27 are
separated from each other. The connection conductor 27 is opposed
to the internal electrode 19 in the first direction D1. The
plurality of via conductors 37 is connected with the internal
electrode 19 and the connection conductor 27.
The connection conductor 27 is electrically connected with the
internal electrode 23 through a plurality of via conductors 39. The
connection conductor 27 is opposed to the internal electrode 23 in
the first direction D1. The plurality of via conductors 39 is
connected with the connection conductor 27 and the internal
electrode 23.
The external electrodes 13a and 13b are electrically connected with
the internal electrode 21 through the plurality of via conductors
31, the connection conductor 25, and the plurality of via
conductors 35. The external electrodes 15a and 15b are electrically
connected with the internal electrode 19 through the plurality of
via conductors 33. The external electrodes 15a and 15b are
electrically connected with the internal electrode 23 through the
plurality of via conductors 33, the internal electrode 19, the
plurality of via conductors 37, the connection conductor 27, and
the plurality of via conductors 39.
Each of the connection conductors 25 and 27 and the via conductors
31, 33, 35, 37, and 39 contain a conductive material. As the
conductive material, Ag, Pd, or an Ag--Pd alloy is used, for
example. Each of the connection conductors 25 and 27 and the via
conductors 31, 33, 35, 37, and 39 is composed as a sintered body of
a conductive paste containing the above conductive material. Each
of the connection conductors 25 and 27 has an approximately
rectangular shape. The via conductors 31, 33, 35, 37, and 39 are
formed by sintering the conductive paste filled in through-holes
fouiied in the ceramic green sheets for forming the corresponding
piezoelectric layers 17a, 17b, and 17c.
Conductors electrically connected with the internal electrodes 19
and 23 and conductors electrically connected with the internal
electrode 21 are not disposed on the principal plane 11b of the
piezoelectric element body 11. In the present embodiment, when the
principal plane 11b is viewed from the first direction D1, the
entire principal plane 11b is exposed. The principal planes 11a and
11b are natural surfaces. The natural surface is a plane
constituted by a surface of crystal grains grown by firing.
Conductors electrically connected with the internal electrodes 19
and 23 and conductors electrically connected with the internal
electrode 21 are also not disposed on each of the side surfaces 11c
of the piezoelectric element body 11. In the present embodiment,
when each of the side surfaces 11c is viewed from a direction
orthogonal to the side surface 11c, the entire side face 11c is
exposed. In the present embodiment, the side surfaces 11c are also
natural surfaces.
The wiring board 40 has a resin film 41, a plurality of conductors
43 and 45, and a coating film 47. In the present embodiment, the
wiring board 40 is provided with the pair of conductors 43 and 45.
The wiring board 40 is, for example, a flexible printed circuit
board (FPC).
The resin film 41 has a pair of principal planes 41a and 41b
opposed to each other. The resin film 41 has electrical insulation
properties. In the present embodiment, the principal plane 41b is
entirely exposed when the principal plane 41b is viewed from a
direction in which the principal plane 41a and the principal plane
41b are opposed to each other. The resin film 41 contains, for
example, a polyimide resin.
The pair of conductors 43 and 45 is disposed on the resin film 41
(principal plane 41a). The conductor 43 and the conductor 45 extend
in a predetermined direction. The conductor 43 and the conductor 45
are separated from each other in a direction intersecting with a
direction in which the conductors 43 and 45 extend. Each of the
conductors 43 and 45 contains, for example, copper.
The coating film 47 is disposed on the conductors 43 and 45 in such
a way as to cover a part of the conductors 43 and 45. Both ends of
the conductors 43 and 45 in the direction in which the conductors
43 and 45 extend are exposed from the coating film 47. The coating
film 47 is also disposed on the principal plane 41a in such a way
as to cover a region exposed from the conductors 43 and 45 on the
principal plane 41a. Both end portions of the resin film 41 in the
direction in which the conductors 43 and 45 extend are also exposed
from the coating film 47. The coating film 47 is in contact with
the conductors 43 and 45 and is in contact with the resin film 41
(principal plane 41a). The resin film 41 and the coating film 47
are bonded to each other in a region where the resin film 41 and
the coating film 47 are in contact with each other. The coating
film 47 contains, for example, a polyimide resin. For example, gold
flash plating is applied to the both ends of the conductors 43 and
45 exposed from the coating film 47.
The length of the wiring board 40 (the thickness of the wiring
board 40) in the direction in which the principal planes 41a and
41b are opposed to each other is defined with a total of the length
of the resin film 41 (the thickness of the resin film 41) in this
direction, the length of the conductors 43 and 45 (the thickness of
the conductors 43 and 45) in this direction, and the length of the
coating film 47 (the thickness of the coating film 47) in this
direction. In the present embodiment, the thickness of the wiring
board 40 is, for example, 70 .mu.m.
The diaphragm 50 includes a metal and has principal planes 50a and
50b opposed to each other. The diaphragm 50 contains, for example,
a Ni--Fe alloy, Ni, brass, or stainless steel. The diaphragm 50
(the principal faces 50a and 50b) has a rectangular shape as viewed
from a direction in which the principal plane 50a and the principal
plane 50b are opposed. The length of the diaphragm 50 (the
thickness of the diaphragm 50) in the direction in which the
principal plane 50a and the principal plane 50b are opposed is, for
example, 250 .mu.m.
The piezoelectric element 10 and the wiring board 40 are bonded to
the diaphragm 50. The principal plane 11b of the piezoelectric
element body 11 and the principal plane 50a of the diaphragm 50 are
opposed to each other. The principal plane 41b of the resin film 41
and the principal plane 50a of the diaphragm 50 are opposed to each
other. That is, the principal plane 11b and the principal plane 50a
are bonded to each other. The principal plane 41b and the principal
plane 50a are bonded to each other.
In a state where the piezoelectric element 10 and the wiring board
40 are bonded to the diaphragm 50, the first direction D1, the
direction in which the principal plane 41a and the principal plane
41b are opposed, the direction in which the principal plane 50a and
the principal plane 50b are opposed are approximately the same. The
piezoelectric element 10 is disposed in a central portion of the
diaphragm 50 as viewed from the first direction D1.
For example, a resin (epoxy resin, acrylic resin, or the like) is
used as a member (sometimes simply referred to as "bonding member")
55 for bonding the piezoelectric element 10 and the wiring board 40
to the diaphragm 50. The bonding member 55 does not contain a
conductive filler and has electrical insulation properties.
The four side surfaces 11c of the piezoelectric element body 11 are
also bonded to the diaphragm 50 (principal plane 50a). In the
present embodiment, the principal plane 41b and the four side
surfaces 11c of the piezoelectric element body 11 are entirely
covered with the bonding member 55.
The space between the principal plane 11b and the principal plane
50a (the thickness of the bonding member 55 located between the
principal plane 11b and the principal plane 50a) is, for example, 7
.mu.m. The space between the principal plane 41b and the principal
plane 50a (the thickness of the bonding member 55 located between
the principal plane 41b and the principal plane 50a) is, for
example, 10 to 30 .mu.m. The thickness of the bonding member 55
located between the principal plane 41b and the principal plane 50a
is larger than the thickness of the bonding member 55 located
between the principal plane 11b and the principal plane 50a.
The piezoelectric element 10 and the wiring board 40 are adjacent
to each other on the diaphragm 50. The wiring board 40 is adjacent
to the one side of the principal plane 11a along which the four
external electrodes 13a, 13b, 15a, and 15b are disposed as viewed
from the first direction D1. The piezoelectric element 10 and the
wiring board 40 are separated from each other as viewed from the
first direction D1. The space between the piezoelectric element 10
and the wiring board 40 is, for example, 1 mm.
The direction in which the conductors 43 and 45 extend and the one
side along which the four external electrodes 13a, 13b, 15a, and
15b are disposed intersect with each other as viewed from the first
direction D1. In the present embodiment, the direction in which the
conductors 43 and 45 extend and the one side along which the four
external electrodes 13a, 13b, 15a, and 15b are disposed are
approximately orthogonal to each other.
As illustrated in FIGS. 1 to 3, the vibrating device 1 includes a
connecting member 61 that electrically connects the external
electrodes 13a and 13b and the conductor 43, and a connecting
member 63 that electrically connects the external electrodes 15a
and 15b and the conductor 45.
The connecting member 61 has one end portion 61a connected with the
plurality of external electrodes 13a and 13b and another end
portion 61b connected with the conductor 43. The other end portion
61b of the connecting member 61 is connected with one end portion
of the conductor 43, the one end portion being exposed from the
coating film 47. The conductor 43 is electrically connected with
the internal electrode 21 through the connecting member 61, the
external electrodes 13a and 13b (external electrode 13), the
plurality of via conductors 31, the connection conductor 25, and
the plurality of via conductors 35.
The connecting member 63 has one end portion 63a connected with the
plurality of external electrodes 15a and 15b and another end
portion 63b connected with the conductor 45. The other end portion
63b of the connecting member 63 is connected with one end portion
of the conductor 45, the one end portion being exposed from the
coating film 47. The conductor 45 is electrically connected with
the internal electrode 19 through the connecting member 63, the
external electrodes 15a and 15b (external electrode 15), and the
plurality of via conductors 33. The conductor 45 is further
electrically connected with the internal electrode 23 through the
plurality of via conductors 37, the connection conductor 27, and
the plurality of via conductors 39.
The connecting members 61 and 63 contain a conductive resin. The
conductive resin layer contains a resin (for example, a
thermosetting resin) and a conductive material (for example, a
metal powder). As the metal powder, for example, Ag powder is used.
As the thermosetting resin, a phenol resin, an acrylic resin, a
silicone resin, an epoxy resin, or a polyimide resin is used, for
example. The hardness of the connecting members 61 and 63 is
smaller than the hardness of the bonding member 55.
The connecting member 61 is disposed on the bonding member 55 in
such a way as to be in contact with the external electrodes 13a and
13b and one end portion of the conductor 43. The connecting member
63 is disposed on the bonding member 55 in such a way as to be in
contact with the external electrodes 15a and 15b and one end
portion of the conductor 45. The connecting members 61 and 63 are
in contact with the bonding member 55.
When voltages having different polarities are applied to the
external electrodes 13 (13a and 13b) and the external electrodes 15
(15a and 15b) through the conductors 43 and 45, an electric field
occurs between the internal electrode 21 and the internal
electrodes 19 and 23. A region in the piezoelectric layer 17b, the
region being sandwiched between the internal electrode 19 and the
internal electrode 21, and a region in the piezoelectric layer 17c,
the region being sandwiched between the internal electrode 21 and
the internal electrode 23 serve as active regions, and displacement
occurs in the active regions. When an AC voltage is applied to the
external electrodes 13 and 15, the piezoelectric element 10 repeats
expansion and contraction in accordance with the frequency of the
applied AC voltage. Since the piezoelectric element 10 and the
diaphragm 50 are bonded to each other, the diaphragm 50 performs
flexural vibration integrally with the piezoelectric element 10 in
accordance with the repetition of expansion and contraction in the
piezoelectric element 10.
As described above, in the present embodiment, the diaphragm 50
includes a metal. The diaphragm 50 including a metal has a higher Q
value and strength than a diaphragm made of glass. Therefore, the
displacement amount of the vibrating device 1 is improved.
The piezoelectric element 10 is disposed in the central portion of
the diaphragm 50 as viewed in the first direction D1. Therefore, in
the vibrating device 1, the displacement of the piezoelectric
element 10 is efficiently transmitted to the diaphragm 50.
The external electrodes 13 and 15 (13a, 13b, 15a, and 15b) are
disposed not on the principal plane 11b but on the principal plane
11a. The principal plane 11b is bonded to the diaphragm 50.
Conductors electrically connected with the internal electrodes 19,
21, and 23 are not disposed on the principal plane 11b. The
external electrodes 13 and 15 (13a, 13b, 15a, and 15b) are
separated from all the edges of the principal plane 11a as viewed
from the first direction D1. As a result, even when the diaphragm
50 includes a metal, the piezoelectric element 10 (external
electrodes 13 and 15) and the diaphragm 50 are electrically
insulated. Therefore, a short circuit between the piezoelectric
element 10 and the diaphragm 50 is less likely to occur, and the
electrical reliability of the vibrating device 1 is improved.
The piezoelectric element body 11 has the four side surfaces 11c,
and the internal electrodes 19, 21, and 23 are not exposed to the
side surfaces 11c. Therefore, in the vibrating device 1, the
piezoelectric element 10 and the diaphragm 50 are further reliably
electrically insulated.
The external electrodes 13a, 13b, 15a, and 15b are separated from
all the edges of the internal electrodes 19, 21, and 23 as viewed
from the first direction D1. Therefore, in the vibrating device 1,
the external electrodes 13a, 13b, 15a, and 15b are further
separated from the edge of the principal plane 11a as viewed from
the first direction D1. As a result, the external electrodes 13a,
13b, 15a, and 15b and the diaphragm 50 are further reliably
electrically insulated.
The two external electrodes 13a and 13b electrically connected with
the internal electrode 21 are adjacent to each other on the
principal plane 11a. The two external electrodes 13a and 13b are
electrically connected with the conductor 43 through the connecting
member 61. The two external electrodes 15a and 15b electrically
connected with the internal electrodes 19 and 23 are also adjacent
to each other on the principal plane 11a. The two external
electrodes 15a and 15b are electrically connected with the
conductor 45 through the connecting member 63. Therefore, in the
vibrating device 1, the electrical connection reliability between
the piezoelectric element 10 and the wiring board 40 is
improved.
Each of the principal planes 11a and 11b has a rectangular shape as
viewed from the first direction D1. The four external electrodes
13a, 13b, 15a, and 15b are disposed along only one side of the edge
of the principal plane 11a. Therefore, in the vibrating device 1,
electrical connection between the four external electrodes 13a,
13b, 15a, and 15b and the wiring board 40 (conductors 43 and 45) is
easily realized.
The two external electrodes 13a and 13b are electrically connected
with the conductor 43 through the connecting member 61. The two
external electrodes 15a and 15b are electrically connected with the
conductor 45 through the connecting member 63. Therefore, in the
vibrating device 1, electrical connection between the two external
electrodes 13a and 13b and the conductor 43 is easily realized.
Electrical connection between the two external electrodes 15a and
15b and the conductor 45 is easily realized.
The side surfaces 11c of the piezoelectric element body 11 are
bonded to the diaphragm 50. Therefore, in the vibrating device 1,
the bonding strength between the piezoelectric element 10 and the
diaphragm 50 is improved. Therefore, the displacement of the
piezoelectric element 10 is efficiently transmitted to the
diaphragm 50.
The member (bonding member) 55 that bonds the piezoelectric element
10 and the diaphragm 50 does not contain a conductive filler.
Therefore, in the bonding member 55, the resin component contained
in the same volume is larger and the adhesive strength is higher
than those of a bonding member containing the conductive filler.
Therefore, in the vibrating device 1, the bonding strength between
the diaphragm 50 and the piezoelectric element 10 is increased.
No member other than the bonding member 55 exists between the
piezoelectric element 10 and the diaphragm 50. Therefore, the
displacement of the piezoelectric element 10 is more efficiently
transmitted by the diaphragm 50.
The piezoelectric element 10 is electrically connected with the
wiring board 40 disposed on the diaphragm 50 on which the
piezoelectric element 10 is disposed. Therefore, a difference in
height between the external electrodes 13 and 15 (13a, 13b, 15a,
and 15b) and the conductors 43 and 45 in the first direction D1 is
smaller than that in the following vibrating device for comparison.
Therefore, in the vibrating device 1, a mechanical load acting on
the connecting members 61 and 63 is low. As a result, reduction in
electrical connection reliability between the external electrodes
13 and 15 and the conductors 43 and 45 via the connecting members
61 and 63 is suppressed. In the vibrating device for comparison,
external electrodes 13 and 15 and a conductor formed on a diaphragm
50 through an insulating thin film are electrically connected via a
conductive resin.
The piezoelectric element 10 and the wiring board 40 are separated
as viewed from the first direction D1. Therefore, in the vibrating
device 1, shape change of the connecting members 61 and 63 is
gentle as compared with the vibrating device in which the
piezoelectric element 10 and the wiring board 40 are in contact
with each other. Therefore, the mechanical load acting on the
connecting members 61 and 63 is lower.
The connecting members 61 and 63 are disposed on the member 55 that
bonds the piezoelectric element 10 and the diaphragm 50. Therefore,
in the vibrating device 1, the connecting members 61 and 63 are
easily formed.
The hardness of the connecting members 61 and 63 is smaller than
the hardness of the member 55 that bonds the piezoelectric element
10 and the diaphragm 50. Therefore, in the vibrating device 1, the
connecting members 61 and 63 are easily deformed in accordance with
the displacement of the piezoelectric element 10, as compared with
the vibrating device in which the hardness of the connecting
members 61 and 63 is equal to or more than the hardness of the
member 55 that bonds the piezoelectric element 10 and the diaphragm
50. As a result, reduction in electrical connection reliability
between the external electrodes 13 and 15 and the conductors 43 and
45 via the connecting members 61 and 63 is suppressed.
The embodiments of the present invention have been described. The
present invention is not necessarily limited to the above-described
embodiments, and various modifications can be made without
departing from the gist thereof.
The number of the internal electrodes, the number of the
piezoelectric layers 17a, 17b, 17c, and 17d, and the number of the
external electrodes 13 and 15 (13a, 13b, 15a, and 15b) included in
the piezoelectric element 10 are not limited to the numbers
disclosed in the above-described embodiment.
The member 55 that bonds the piezoelectric element 10 and the
diaphragm 50 and the member 55 that bonds the wiring board 40 and
the diaphragm 50 may be the same member or different members.
The diaphragm 50 may be a casing of an electronic device or the
like. The diaphragm 50 may be a separate member from the casing of
an electronic device or the like. In this case, the diaphragm 50
may be attached to the causing by surface bonding.
* * * * *